1. Field of the Invention
The present invention relates generally to polyimides. In particular, it relates to polyimides containing siloxane groups, especially pendent siloxane groups.
2. Description of the Related Art
Polyimides (PI) comprise a large family of heterocyclic polymers which were first prepared in the late 1950s. Since then a large volume of information has been generated concerning the synthesis, characterization, use, physical and mechanical properties of these polymers. There are a number of reports concerning polyimides containing siloxane groups in the main-chain (i.e., polymer backbone). A patent describing polyimides containing siloxane groups in the backbone dates back to 1961, (D. L. Bailey and M. Pike, U.S. Pat. No. 2,998,406 to Union Carbide Corporation). These polymers were first described in the open literature in 1966, [V. H. Kuckertz, Die Makromolekular Chemie, 98, 101 (1966)], and they were prepared from 1,3-bis(3-aminophenyl)-1,1,3,3-tetramethyldisiloxane and pyromellitic dianhydride. Another paper involved the preparation of silicon containing dianhydrides and their subsequent reaction with aromatic diamines to form polyimides, [J. K. Gilliam and H. C. Gilliam, Polymer Engineering and Science, 13(6), 447 (1973)]. Other papers that followed include: I. Yilgor, E. Yilgor, B. C. Johnson, J. Eberle, G. L. Wilkes and J. E. McGrath, Polymer Preprints, 24(2), 78 (1983); S. Maudal and T. L. St. Clair, International Journal of Adhesion and Adhesives, 4(2), 87 (1984); B. C. Johnson, I. Yilgor and J. E. McGrath, Polymer Preprints, 25(2), 54 (1984); A. Berger, Society for the Advancement of Material and Process Engineering Series, 30, 64 (1985); and C. J. Lee, Ibid., 30,52 (1984).
Some United States patents that pertain to polyimides containing siloxane groups in the main chain include: F. F. Holub, U.S. Pat. No. 3,325,450 (1973); J. T. Hoback and F. F. Holub, U.S. Pat. No. 3,740,305 (1973); A. Berger, U.S. Pat. No. 4,011,279 (1977); H. Ryang, U.S. Pat. No. 4,404,350 (1983), all assigned to The General Electric Corporation; H. Sato, U.S. Pat. No. 4,395,426 (1982) to Hitachi Chemical Co. Ltd.; and A. Berger, U.S. Pat. No. 4,395,527 (1983) to M & T Chemicals, Inc. All of the above mentioned related art pertain to polyimides containing siloxanes in the polymer backbone.